Reversible electronic code translators



May 8, 1956 A. E. CANFORA ETAL 2,744,955

REVERSIBLE ELECTRONIC CODE TRANSLATORS Filed Aug. 24, 1953 5 Sheets-Sheet l BY/(M 745 /www RNEY May 8, 1956 A. E. CANFORA ETAL 2,744,955

REVERSIBLE ELECTRONIC CODE TRANSLATORS Filed Aug. 24, 195:5 5 sheets-sheet 2 Jia,

INM/$70125 ORNEY May 8, 1956 A. E. CANFORA ETAL 2,744,955

REVERSIBLE ELECTRONIC CODE TRANSLATORS Filed Aug. 24, 1953 5 Sheets-Sheet 3 iii AWT UKE. CHA/F099 d ORNEY May 8, 1956 A. E. CANFORA F-'TAL 2,744,955

REVERSIBLE ELECTRONIC cons TRANsLAToRs Filed Allg. 24, 1953 5 Sh9BtS-Sh8Bt 4 ORNE Y May 8, 1956 A. E. CANFORA ErAL. 2,744,955

REVERSIBLE ELECTRONIC CODE TRANsLAToRs Filed Aug. 24, 1953 5 Sheets-Sheet 5 ORNEY United States Patent REVERSIBLE ELECrRoNrC CODE TRANsLAToRs Arthur Eugene Canfora, Brooklyn, N.l Y., Anthony Liguori, Hackensack, and Eugene Richard Shenk, Bergenteld, N. J., and Hajime James Kish-i, New York, N. Y., assignors to Radio Corporation of America, a corporation of Delaware Application August 24, 1953, Serial No. 375,995

16 Claims. (Cl. 178,-23)

The prior art printing telegraph equipment makes use of a fixed-length code, in which a predetermined number of units of time are allotted to each transmitted character, exclusive of start and stop pulses. Each time unit will be referred to hereinafter as a signal element or as a baud element or baudel. A specilic character will be designated, depending on whether these baud elements contain tone corresponding to mark or no tone corresponding to space. For example, in the conventional -unit printer code the letter A is composed of baud elements l and 2 marking and baud elements 3, 4 and 5 spacing. One or all of the baud elements may be marking, depending on the character being transmitted.

As stated above, a character expressed in the 5-unit code could contain from zero to ve marking elements. In transmission, particularly over radio circuits, some marking elements may be deleted and some spacing elements may be iilled in by noise. The result is the recording of a false character, which can be serious in coded-word transmissions. A safety or protected code has been devised which requires the transmission of a predetermined number of baud elements for each character, a lixed number of which are marking. The reception of seven elements or baudels containing more or less than three marking elements can be made to prevent an error misselection from being processed as a legitimate character, either by printing a misselection symbol in place of the mutilated character or, preferably, requesting a repeat of the transmission. For this reason such a protected code is often called an error detecting code and is sometimes referred to as a safety code.

Because of the extensive use of 5-unit equipment throughout the world, it is more economical, if not an absolute necessity as well, to use this type of terminal equipment, and at the same time retain the error indicating features of the 7-unit protected code for transmission over radio circuits. Previous'methods of code translation, in the main, have utilized either multi-contact relays or other mechanical means. These methods indirectly bring about serious disadvantages in slowness of operation and excessive maintenance of contacts which must be kept in working order at appreciable expense and difhculty. Electronic code translators have been suggested for both telegraph and accounting systems. An excellent discussion of such prior art arrangements is given in chapter l2 of the The Design of Switching Circuits by Keister and others of Bell Laboratories 1950 and in several copending U. S. patent applications. Examples of such U. S. patent applications are Serial No.

272,825, tiled February 21, 1952, on behalf of Arthur ICC E. Canfora for an Electronic Code Converter, now abandoned and Serial No. 361,979, tiled .Tune 16, 1953, for a Code Converter System, now patent No. 2,724,739, issued November 22, 1955, Serial No. 364,074, filed lune 25, 1953, for a Code Converter, now U. S. Patent No. 2,716,156 dated August 23, 1955, Serial No. 368,973, led July 20, 1953 for a Validity Checker, now U. S. Patent No. 2,688,050 dated August 31, 1954, on behalf of James S. Harris. For the most part these prior art arrangements are not suiciently flexible for application to a number of systems without extensive revision and are limited to translation in one direction only.

An object of the invention, therefore, is to translate code characters as expressed in a given fixed-length code to the corresponding characters as expressed in any other fixed-length code by improved electronic means.

A more specific object of the invention is to provide a simplified electronic code translator which can be reversed to translate from a given code lto a predetermined code or conversely by manipulation of a single switching element.

A further object of the invention is to provide a reversible code translator which can accommodate any two fixed-length codes by interchanging a small portion of the circuitry as an integral unit.

It is a feature of the invention that characters expressed in any fixed-unit code may be translated into any 'vidually applied to energize the storage elements according to the nature of the signal element assigned.

A further plurality of bistable reciproconductive circuits, one for each signal element of a character as expressed in the outgoing code are interconnected as a binary counting chain, and coupled to an astable reciproconductive circuit or other form of pulse generator. The storage elements and the binary counting chain are coupled by a plurality of resistive elements connected to the output terminals of each of the storage elements and bistable reciproconductive circuits in such permutationsvas to establish a plurality of coincidence voltage points, there being one such coincidence voltage point established for each character to be translated. 'I'he coincidence voltage points are individually coupled to the input electrodes of a number of unilateral impedance coincidence detector devices, such as vacuum tubes, transistors or germanium diodes. The output electrodes of the coincidence detector devices are all connected to a gating circuit which, in turn, is coupled to the pulse generator.

After the storage means are reset to the initial condition and 'the input signal elements for the character under consideration are established in the storage elements, an operate pulse is applied to the pulse generator to start the conversion process. The train of pulses produced by the pulse generator is applied to the counting input of the binary counting chain, which operates in the conventional binary or scale-of-two counting chain fashion with the tubes of each reciproconductive circuit conducting or blocking in accordance with the number of successive pulses that have been applied at any given time` As soon as the tubes in the binary counting chain are conducting in accordance with the elements of the character under consideration, as expressed in the translation corresponding to the signal elements of the character under consideratiomkas set up in the storage elements, a unidirectional potential' will be set up at one otthe coincidence voltage points, which is opposite in polarity to all of the potentials at every other coincidence point. Preferably this potential will be, positive and. will cause the corresponding coincidence detector device to conduct.

or otherwise change the. modeV of operation., Only one, of these coincidence devices is operated for any one coded character, therebeing separate devices for each character. Thef operated coincidence device changes conductivity of the gating circuit to blockthe pulse` genera tor..` The reciproconductive circuits in the binary counting chain are now left, conducting in accordance, with the signal elements of the character under consideration, as expressed in they code as translated,y andare ap-v plied to any suitable utilization means.. After each character is translated, a reset pulse is applied to the storage elements, restoring them to the initial', condition. This reset function, of course, is performed automatically where the signal elements are of actively opposing nature, butl is required where one nature is represented by an active current ow and' the other by absence of such current flow.

'A translator according to the invention may be arranged to handle any two fixed-length codes by changing the coincidence connections. One suggested arrangement is that of a plugin type mounting for the isolating resistors` and the coincidence. detectors havingone set of' terminals for connection to one counting chain, another set of terminals for connection to the other counting chain, and a further set of terminals for connection to the pulse. generator control gate.

According toithe invention a reversible codetranslator is -realized by using bistable reciproconductive circuits for the storage elements with interconnections to form ar'xotherr binary counting chain andV interchanging the connections between the pulse generator and the binary counting chains, together with the reset circuitry, so that when the input signal elements are applied to the first mentioned binaryl counting chain, ithe second. chain is advanced through the various permutations by the oscillator toy establish coincidence for the character un.- der consideration, exactly asl described before with referencel to the 'rst mentioned binary counting chain. A simplemulti-pole double-throw switch is suilicent to switch the circuits for translation in one direction orV the other;

Further, in accordancewit-h one aspect of the invention, the resetcircuit arrangement is used: toset upv one orl more. prearranged'. code characters in the outgoing binaryV cidence detector to resolve ambiguities arising from the omission of certain component parts of the basic ar rangement of the invention.

In order that the invention may be more clearly understood and readily put to practical use, a circuit arrangement embodying the invention is hereinafter described, by way of example. only, with reference. to. the. accompanying drawing in which:

Figi l is a functional diagram of a basic elect-ronicc.o.de translating'circnit arrangement accordingto the. invention; and

Fig. 2 (sections a, b, c.: and d being taken together) is a schematic diagram of an embodiment of' a reversible electronic code translatingcircuit. arrangement, according to the invention.

Referring to Fig. 1, there is shown a functional diagram of the electronic code translator according to the invention. A character as expressed in a givenV codev is applied to the coding terminals 11. oi a plurality of storage elements, preferably n stages of' bistable reciproconductive circuits interconnected as an n-element binary counting 'chain 13. As employed' herein, the term reciproconductive circuit is construed to include all twotube, regenerative devices, in which conduction alternates in one or the other tube in response. to applied triggering potential. The term multivibrator is frequently applied' to this circuit and the term locking circuit. is sometimes applied to a bistable reciproconductive circuit, whichis'oney inA which two triggers are required to, switch from one stable state to the other and return. The bistable reciproconductive circuits may be further distinguished as binary reciproconductive circuits which have a single input' terminal and reverse the state of conduction each timel a trigger isv applied and as lock-in reciproconductive circuits which have two input terminals and require alternate input triggering in ord-er' to reverse the state of conduction. According to the invention either typeV of bistable reciproconductive circuit-may be used nthel counting chains, although for reasons later given the lock-in type is preferred. In the counting` chain 1'3, there is actually a separate codingl terminal for` each reciproeonductivecircuit stage, aswell asl the single conventional counting input terminal 15t for the cascade of stages. The reciproconductive circuits4 of theY counting chain 13 may be reset to a prearranged state of conduction under` the influence of a resetA control circuit 17? acting in response to a reset pulse applied to the terminal 19.". The character under consideration as excounting chain'as. required for operational signa-ls irl/cera tain automatic telegraph code signalling systems; More particularly this-resetting is accomplished by means of a reset circuitv arrangement wherein the leading edge of a` reset. pulse is employed; to trigger the reset circuit to: place all of the electron discharge devices aidectedV in the initialstates oiV conduction. and the. trailing edge. of the; same reset pulse is utilized to trigger those electron dischargel devices to the opposite state of conduction neces sary to establish the prearranged code character .desired inthe storage bank.V

VWhere a protected code is used, one or more further coincidence points arey established by resistive isolation means as. described above in such permutations that the points change4 polarity with` respect to av predetermined circuit. point, as the proper ratio of spacing-to. marking;

signal elements. present in each character of the protected.

In` an alternate embodiment of the, invention thevalidity detector is used. in conjunction', with the. coin.'-

pressed ina predetermined code is read out atv the coding terminals 21 of an' frz-elementbinaryl counting chain 23 having m stages of bistable reciproconductive circuits'. also connected in the conventional binary or scale-of-two counting chain circuit. Againthere is a separate coding terminal for each reciproconductivecircuit- :stageg. as` wel-1E as the conventional counting terminal" 2S. According to the invention m and n may be any integersf and may, if desired, eveny be the same integer. The. reset control circuit 17- may also be used, if desired,

toreset. the 11i-element chain 23 to a prearranged state of conduction.v f

Twoi leads, one from` each of the reciproconductive stages-fof the binary counting chainsrlS and 23, are connected. to-, acoincidence. detector circuit 27 arranged to establish a predetermined current. relationship, when theconduction of theA stages of the n-element chain 13 correspond tothe conduction of the stages of the m-element chain 23'.. Apulse generating` circuit 31, controlled by a generator gating circuit33, is. coupled tothe. m-element binary counting chain 23.` at the countingy terminal 25. An operating` orconvert pulse is applied to the gener ator'gatecircuit 33,` at anY input terminal 35'` to start the pulse generator 3l.. The coincidence detector 27 is coupled.v to the; generator gate 33y toturn the-pulse generator off' in response; to. coincidence as indicated by' thepredetermned current relationship.

The circuit arrangement, as thus far described,l may b e reversed totranslate a character expressed -in the predetermined code into the given code by switching the pulse generator 31 from the counting terminal 25 to the counting, terminal and applying the signal elements of the predetermined code to the coding terminals 21. Upon coincidence being established, as described above, the signal elements of the character under consideration can be read out in the given code at the coding terminals 11.

Where a protected code is in use, a further coincidence circuit or error detector 37 is coupled to the binary counting chain 13, as shown in Fig. l, for the protected code. This detector 37 is arranged to determine the coincidence of the proper ratio of marking signal elements to spacing signal elements. When such coincidence is established, the-gate 33 is arranged to stop the pulse generator 31 in response to the operation of the coincidence detector 37. When an invalid signal element combination is scanned, the gate 33 is held open under the influence of the error detector 37 and the pulse generator 31 continues to step the -protected code chain 13 until a valid constant ratio code character is determined. At the receiving end of a telegraph signalling system incorporating a code translator according to the foregoing description, an indication of mutilationof the received character signals is set up in'the error detector 37, at the error output terminal 39, which is used, either to print an error symbol or to holdup the translating process and call for a repetition of the character by the source as desired in some automatic telegraph signalling systems.

Referring to Fig. 2 there is shown a reversible circuit arrangement specically designed for translating from the tive unit printer code to a seven unit protected code and conversely. Obviously, conversion of any -fixed unit code to any other fixed unit code Will be possible in accordance with the basic principles of the invention as set forth hereinafter.

Referring particularly to sections b, c and d of Fig. 2 there are shown five coding terminals 11-1 through 11-5 connected to individual storage elements, shown here as bistable reciproconductive circuits 51-5S. While capacitors or magnetic structures or other simple devices may be used for the storage elements according to the invention, some form of triggered electronic storage element is preferably used, and for reasons which will become obvious later, the reciproconductive circuit is preferred. Initially, the storage elements in the form of reciproconductive circuits 51-55 are set to the initial condition wherein the A tubes of each of the circuits are blocked and the B tubes are conducting. If the code character elements to be stored were in the form of energy of dierent nature or level, such as a positive potential for mark and a negative potential for space, this would not be necessary. The circuit arrangement of Fig. 2 is designed for the application of energy for elements of one nature and the absence of energy for elements of the other nature. In this case potentials corresponding to the marking signal elements of a code character are applied individually to the coding terminals 11-1 through 11-5. The respective reciproconductive circuits 51-55 are then triggered and remain energized in accordance with the nature of the signal elements assigned to each reciproconductive circuit. Until reset these reciproconductive circuits 51-55 serve to store the character under consideration as indicated by the state of conduction of each of the reciproconductive circuits. y

The anodes ofthe tubes VSA through V12B are indil minals 21--1 through 21--7. The signal elements established at the further coding terminals 21-1 through 21-7 are intended to remain for a time period long enough to enable the associated apparatus to read out the intelligence and perhaps also to perform other functions. For this reason, it is desired that some type of storage element be used, and, therefore, a plurality of bistable reciproconductive circuits 71 through 77 are individually connected to the further coding terminals 21-1 through 217. The reciproconductive circuits 71-77 are shown as being identical in design and circuit components to the first mentioned reciproconductive circuits 5 1-55, though this need not necessarily be so in order to practice the invention. The reciproconductive circuits 71-77 are interconnected in cascade by means of capacitors 79 to form a binary counting chain. The outputs ot the individual reciproconductive stages 71-77 are connected to a plurality of busses 81-87. According to the basic principles of the invention, 14 busses would be required as explained in connection with reciproconductive stages 51-55 and the busses 61a through- 6512. However, due to a further aspect of the invention only seven busses are required for use with the protected seven-unit code. The seven busses 81-87 are interconnected to the five-unit busses 61a through 65b by means of resistors 5A1 through SAS, 5B1 through SBS and so on, and resistors 7A1 through 7A3, 7B1 through 7B3, and so on in such permutations as to form one coincidence point at the common junctions of each group of resistors for each character to be translated from one code into the other. According to the basic principles of the invention, n-resistors are required for the n-element code and m-resistors are required for the m-element code. In the example shown there are five resistors for the Vfive-unit code, but instead of seven resistors for the seven-unit code, only three resistors are required because the latter code is of the protected variety. The resistors actually used are those connected to those busses which represent the signal elements of a given nature, in this instance marking elements, and the ambiguities inherent in such a short-circuit arrangement are resolved in conjunction with the operation of the error detector 37 as later explained. The potentials applied to the reciproconductive circuits and those subsequently applied to the busses are chosen so that if any one of these busses coupled by resistors to the coincidence point contributes a negative voltage, the coincidence point will not go positive. Thus, the seven-unit arrangement as shown involves fewer resistors and provides larger steps of voltage at the coincidence points. Only one coincidence point is established for each of the characters involved. In the example shown eight such coincidence points A through H corresponding to the respective letters of the alphabet are established. According to the invention, each coincidence point is connected to the input electrode of a coincidence detector device. A triode vacuum tube, connected either as shown for the tube V20A or the tube V22A, makes an excellent coincidence detecting device and a high vacuum diode device could also be used to advantage. In the circuit arrangement shown, however, 35 such triodes or diodes would be required to handle the total number of characters to be translated. Considerable savings in iilament power is effected by utilizing cold cathode triode or diode elements, such as gaseous discharge devices, transistors or germanium diodes. In the circuit arrangement of Fig. 2 germanium diodes are shown for the detection devices D1A, D3B and so forth. Further, clamping diode elements D2, D4 and D6 and so forth are connected from the input electrode of the coincidence detecting diodes DIA, DSB and so on, to a point of negatvie potential as indicated by the minus sign. These clamping diodes are used to prevent the large negative voltages, that would appear at the coincidence points in the absence of the clamping diodes, from appearing across the coinci-y arca-955 7,. dence detecting diodesv and consequently nullifying the one; positive voltage which. shouldi appear on-thecom mon-outputlead. Thesex clampingv diodes are necessary wherethe detection devices are germanium diodes;` or the like, having finite back resistance componentsa The need-for-'suchclampingdiodes is obviated, if; the coincidencedetecti'on devices are vacuum-tube diodes ortriodes with practically infinite baclt resistance components. Only eight coincidence circuits are shown' in Fig.. Z, sec-- tionsf b, c and d; The; output electrodes off thel eoinci dence detector diodes D'lA, DSB, and soon, as previously mentioned, are connected in common tothe grid of an isolating triod'e tube- VZOA. Twenty-four of the remaining coincidence points aredivided among threel additional triode vacuum tubes VZGB, V21Ai andx V21-B`. These vacuum tubes are used to-scparate` the coincidence circuitsirrto. groups wherebylarger4 differential voltages may be used inl order to obtain the` desired coincidence selection. If" vacuum tube coincidence detectorswere used', the tubes V20`A through V213 would non be used asisolating'tubes; Instead these tubes and others would beconnected inparallel as' shown except thatthe gridsv Wouldbe individually connectedto the coincidencevolt agepoints', A, B, C, and' so on. Dividing the load'presentedby'the coincidence devices into groups willl reduce the'imped'ance presented'acrossthevsubsequent input circuit;

The cathode and anode elements of4 tubes V-ZOA through V21B` are connected inparallel and the tubesare` coupled toi the grid of any inverter-amplier triode vacuumA tube- V16A-. A- similar inverter-amplier triode vacuum tubeA V14B` is coupled to the output of'vacuum tube- VIGA. rThe output of vacuum-tube-V14Bis'cou-- pled-'toa gating-lock-in reciproconductive circuit: 33 com-- prising'vacuum` tubes V-15A and V-15B-crosscouple'd in aconventional bistable lock-in reciproconductivecircuitf conii'guration. The reciproconductive circuit 33 is -inetctav gating-circuit for the-pulse generator 31- accord-- ing-'tothe invention which is shown as an astable reciprofconductive circuit-` cornprising the. tubes VIVA, V1-7B`. A convert pulse or an operate pulse applied to the convertpulse input? terminal 353 isf injected in theA anode circuit ofthe vacuurntube V15Bto open-the generator gate` 33- and the-output ofthetube-V14Blis applied to the-cathode of4 the vacuum tube VISA to close the generator gate 33; Opening andclosing of theegate-33 turns the astable reciproconductive circuit31 onand-otftoproduce a train of'pulses'which are applied tothe-.cathode-follower and impedance transforming' tube VISA. The pulses obtained from thecathode follower tubeE VISA areapplied by'- means of a sWitchSI to the counting-'input' terminal 25 of the m-element binary chain comprising the reciproconductive-circuits 71-77. The application of a convert pulse to the generatork gate- 3?willy start the pulse generator 31 toproducea train of pulses which When applied tothecounting input terminal 25 will advancethe-binary counting chain 23v in the normal counting mode.

When the rst pulse is applied at' the counting terminalZSi the stateo conduction of the tube-V1A of the` reciproeonductive-circuit 71 is reversedand the-tube VIB is likewiseO reversed inA response to the reversal ofthe former' tube; the remainder of the tubes inthe circuit remaining in the initial condition. The second pulse` from theV generatorV 31"- will? restore the reciproconductive circuitA 711 tothe initial' conditionand trigger thereciprocond'uctive circuit 72 to the opposite stable state-condition; theremainder of the tubes inthe chain remaining in the initialcondition-andso-on. As the stages of the counting chain- 23 are advanced in the conventional counting" chainY modevarying potentials will be applied to-the-m-element'busses til- 87; Sbmeof the groups of resistorsl 7A1L-7A-3; 71311-71332 and so forth will have'- at leastoneres-istor'contributing af negative` potential= to thev coincidence point; of the resistors irr` the reemainingf groups will have positive' potentials there'acrcss rendering thel coincidence pointspositiye insofar asl 11i-element-v hnsses are concerned;

When the elements of az five-unit character are pre; lsentediforconversion-at terminals 11`-E through-IL--v one group of resistorswill contribute five-incrementsA ot* positive voltage to the coincidence' point correspondingto* the character' under consideration. Applicationofthe convert pulse to.- the convert input terminal 35 willi openv` the gate- 33'- and cause' the pulse generator 3i' t'o-prodilce a train of pulses Whichare applied-tothe counting termi;- nal 25'I toadvance the reciproconductive circuits 71-77-r through theperrnutedS states of conduction untilv the three resistors of" one set eaclrcontribute'- apositive voltage tothe coincidence point" associated therewith.- Assuming that the proper setl of resistors is selected; coincidence' will be establishedl andthe positive potential will be ap plied through the diode'A coincidence4 detector device`4 to the generator control gate- 331i This will closej the'l gate.' 33andstop-the-pulsegenerator 31 from applying pulses to the'counting chainy 23. The bistable reciproconductive" circuits; 7-1--77 are thenleft in individual conductionJ conditions representative ofvr the respective elementsf of" the character under consideration asexpressed in the'-l codel into which translation is desired. This character will be-stored fr a time sucient to enable any utiliza-- tion device toreadfoutfthe character.

More detailed explanations of theY operation of the coincidence'- ci'rcuit are' to befound in copending U. S; patent applications Seriali No.v 272,825V for Electronic Code Converters-tiled- Fbruary 212, 1952', on behalf of Arthur El Canfora, now abandoned, and Serial No. 279;'432' for Electronic Diplex Transmitting'Distributors, tiled March 29; 1952,` novvv U. S.- Patent No.- 2,682,574;

dated June' 29; 1954 on-behalf'ofA-rthur E; Canfora-and-4 Eugene R. Shank.

It is not necessary to reset the countingchain 23whencountingfto 7lunit codeA because the: scanning process will step-tl1'el counting chain 23 through all ofl the'y conditions blocked and-the grids of all-ofthe B tubesare allowed'tol go positivewith`- respecttothe associated cathod'es-thereby' rendering the tubes conducting tof establish the' initial state of conduction ofy the entire counting chain-With-a'll'v of the A- tubes blocked and allof-th'e B-tubesconducting. Neon`v glow lamps can beconnected to the ano'des-of'thc` 1 A tubesto-provideay visual indication offidlingiconditionif desireda When' converting fromve unit-'to-sevenunitcode, the five unitreciprocond'uctive circuits 51-55` need be reset: only ifi one natureJ of the applied signal elements is= the absence of energy; Since the arrangementlv of Fig: 2'is1 designed for positive markingY and zerospacing voltages; a resetfpulseis obtainedfromithe anode of' the-generatt'n` gatetube V-iand' applied through the switch S1=Y andi counting chain 13. This reset circuit functions exactly as that described forF they seven-unit reciproconduetive circuits'.

unit protected-.code storageA elements-orreciproconcluctive1 circuits 7-1-77' be left with; a denite'- or prearranged character established therein.

theY

When the reset pulse is-y 'lhis resetpulse' is made available at thei ter-- mina-l 69ff'oruse in other apparatus'. It'isfurtlrerfdesir-able that in' some instances the' seven-A For' example;. when.v con;= -L vertingjroma;tive-unit'codetoisevensunitcode f'curtra'n'sa.-l

'9 mission over a radio -relay path, it is highly desirable that the charactera or the character be set up in the counting chain 23 between the message text characters in order to indicate in what service the circuit is being operated. That'is, to indicate to the operator whether tolls are being computed, or the like. The circuit arrangement comprising the reset triodes V19A, V19B and the switch S-2, shown in Fig. 2b, is utilized for this purpose. All of the tubes of the m-element counting chain 23 are first reset` to the initial condition in response to the leading edge of a negative-going reset pulse applied to the terminals 19-1 as described above. The grids of the tubes V3A and V4A are connected to the anode of the service character reset tube V19B to place the voltage at the anode of tube V19B on the grids of tubes V3A and V4A. The control-signal selecting switch S2 also selects either the grid of the tube VSA or the tube V7A for connection to the anode of the reset tube V19B and places the usual negative voltage on the grid of the other tube V7A or VSA respectively. This selection determines whether or not the character a or is placed in storage; the difference between the two characters being only in the time occurrence of the ylast element. A relatively-large capacitor 101 is connected between the anode of the tube V19B and ground. The reset pulse causes this capacitor to be charged so that when the trailing edge of the reset pulse appears, a sharp pulse is applied lto the grids of tubes VSA, V4A and either of the tubes VSA or V7A. The negative-going reset pulse applied to the grid of tube V19A causes a positive going pulse to be applied from its anode, thru switch S1, and thru a capacitor-resistor differentiating circuit to the grid of normally conducting tube V19B. The negative spike from the differentiating circuit occurring at the trailing.

edge of the reset pulse causes the tube V19B to be momentarily cut oit with the result that a positive trigger is applied to the grids of tubes V3A, V4A and either of the tubes VSA or V7A. The reciproconductive stages 73, 74 and either 75 or 77 are thereupon triggered to the opposite condition thereby establishing the desired character in storage until cleared out for the next message text charac-A ter.

When converting from seven-unit into five-unit code another reset pulse is applied at terminal 19-2 to resety the n-element counting chain 13 to the initial condition only in order to extinguish the neon glow lamps 67. If such reset were not made, the last character set up in the counting chain 13 would be indicated. When idling it is preferable to show all elements spacing, hence the reset circuit is preferably included in the circuit arrangement.

With the arrangement set up as shown for converting into a protected code, it is possible to have more than one group of resistors satisfying the coincidence condition during this scanning process because it is possible to have more than three of the bi-stable reciproconductive circuits in the counting chain 23 in a marking condition and contributing positive voltages to the respective coincidence resistors. Once the coincidence condition is satisfied, the

binary counting chain advance will be stopped and conv sequently there will be presented at the output terminals 21-1 through 21-7 an erroneous seven-unit code character consisting of more than three marking elements. To prevent this, an error detector circuit 37 is used. It should be noted that while the detector 37 was shown connected to the counting chain 13 in Fig. l, it is shown connected to the counting chain 23 in Fig. 2 since thev latter chain is the only one in which the protected code is set up. It should be clearly understood that such an,`

error'detector can be connected to either chain if arranged for protected code. The error detector 37 comprises two normally blocked triode tubes V13A and V13B having interconnected anodes and individually biased cathodes. The grid of the tube V13A is connected to the anodes of each' ofthe A tubes in the reciproconductive circuits 71 -77. The bias on the tube V13A is set so that this tube is blocked when the voltages on the resistors 91a,

92a 97a are indicative of three marks or three marking elements, that is, four of these resistors are contributing positive voltage. The grid of vacuum tube V13B is likewise connected to the reciproconductive circuits 71 77 except that the resistors 91b, 92h 97b are connected to the B tubes by way of the busses 81-87. The bias is set on tube V13B so that the tube V13B is also blocked if three of the resistors 911;, 92b, 97b, are producing positive voltage. Since the voltages applied to the grids from the reciproconductive circuits are in effect out of phase, it can be seen that tube V13A is conducting (indicating an erroneous combination) as long as the voltages applied to the grid indicate that there are zero, one or two marking elements, that is, less than three marking elements, and the tube V13B is conducting when there are four or more marking elements. Conduction of either tube V13A or V13B serves to prevent the generator gate 33 from being closed. Since no valid com' bination has less than two marking elements, the functioning of the tube V13A is not important here and its application will be further discussed hereinafter. The tube V13B when conducting maintains the pulse generator 31 in operation until a valid coincidence point is established. With the `use of the error detector circuit as shown, a large number of coincidence point connecting resistors are eliminated and better operation is obtained because wider voltage diierences are available for energizing the busses from a given power supply. The pulse voltage developed by the error detector 37 is purposely made to shunt out the pulse derived from the coincidence detector isolating tubes V20A through V21B so that in the event that an erroneous selection is made the coincidence detector cannot control the gate 33 to stop the pulse generator 31.

The circuit arrangement in Fig. 2 is arranged for use with the five-unit printer code, which has a possible total of 32 ydistinct combinations for assignment to intelligence values, and a protected code of seven units, three of which are always marking or spacing. This protected sevenunit code, which is the most eiiicacious protected code for use with the printer code, from the standpoint of simplicity of apparatus, provides a total of distinct combinations. The three extra combinations may be used to provide an indication of misselection or nonuse, but in many instances these extra combinations are used to elect some change in the operating circuit without affecting any of the tive-unit equipment. In the arrangement shown in Fig. 2, three separate coincidence detectors comprising three triode tubes VZZA, V23A and V22B are used to detect combinations which are not converted into live-unit code. These combinations are used to establish currents at the terminals a, [8 and I. The currents developed at these terminals are then applied to apparatus controlling the operation of associated circuitry. The tube V23B is coupled between the cathodes of all of the extra combination detectors V22A, V23A and VZZB and the error detector amplifier tube V14A by way of an amplier triode V16B. An error output voltage applied to the grid of the tube V16B causes the tube V16B to pass current through the diode D71 to shunt any coincidence pulse that may be presented across the diode D71, thereby preventing any such pulse from closing the gate 33 and locking the oscillator 31. The anode of the tube V16B goes low at the same time to cut ot the tube V23B. This renders the cathodes of the tubes V22A, V22B and V23A high, tends to cut these tubes olf, thereby preventing these tubes from developing any output current.

According to the invention, the circuit arrangement shown in Fig, 2 is reversible, To reverse the circuit the elements of the seven-unit code characters to be translated are applied to the further coding terminals 21-1 through '21-7 and theswitch S-l is thrown to connect the pulse anuencia at'the-codng terminals Li'I--l` through lil-5. The'stonl age'elements et the neelement binary chain' which' areV the reciproconductive' circuits 5dr-55, are interconnectedy by'v means' oh capacitors 9W to' form a binarypcounting chain ofi the same configuration as that' of" thc bmary counting chain 23. Thus the counting chain- 123 is ad'- vanced stageby stage by operation of the pulse generator 31- until= coincidence is established and'- thel pulse generator 311 is blocked. rThe outgoing code is then' setup ati the coding terminals-'11-1E throughlli-5A ofthe' inclement chain 1'3;

Ini accordance with afurther aspect-*oftheY invention, the.y circuit' arrangement of Fig. 2` is constructed* with the coincidence-circuitry assembled on' a plug-in sub-chassis.

Asocket is provided on the main chassis'ha-ving contacts:

connected to the anodes of the tubes V133, VZB, VrB V7B, other contacts connected tothe anodes o-the tubes VSA through V123y and further contacts connected totthe gridsv of .the tubes VZtlA' through V23A.

Thebusses 61a through 6511 and Sii-87 are connected to 1 prongs on a plug corresponding to the socket. The diodes DIA,D2; DSB, D4, DSC, D6v and so-forth, the resistors SA'li-SiASg 5B1-SBSV and so on and the resistors 7A1- 7A3,.7B1'-7B3 andso` on are mounted on the busses` in the-proper permutated connections for the codes involved.

Thus' suchassis can be wired so thatany seven-unit code. can be translated into any tive-unit code and conversely,.simplybychanging the plug-in sub-chassis. Ob-

viously any code having fewer elements can be accom-- including` a plurality of storage circuits-in thel form'v of' input bistable reciproconductive circuits'connected as a binary chain, there beingV one such reciproconductivecircuitiforeach: element of acharacter asl expressedv in the code' to be translated, means responsive'tolcode signals expressed'. inthev code to bev translated, tov trigger said reciproconductive circuits in accordance with'the natureL ofthe signal elements of the character to'be translated, a nurnberf'of output-'bistable reciproconductive circuits, there beingone suchreciproconductive' circuit for each element of? az character as expressed in another code, an astable reciproconductive circuit, a gating'locleinreciproconductiveicircuit coupled to said astable reciproconductivecircuit; normally holding the latter'inoperative by' an appliedholdingr. bias voltage, a source of operate or convert: pulses synchronized with the utilization apparatus', means' to apply said operate or convert' pulses to said ganng reciproconductive circuit to-removesaid bias voltage'. aridfperrnitsaid astable reciproconductive circuit to` runl freely, a' plurality of' coincidencepoints; a plurality' of? resistive elements-connected to coincidence' points, a

plurality of'plural4 electrode electron flow' pathv devices connecting said coincidence-pointsto'said astablereciproconductive circuit, means to apply the output of. saidA astable' reciproconductive circuit to said outputbistable reciproconductivev circuits connected as a binary chain; said'output reciproconductive circuits producing.,voltag es whereby a single one of'said coincidence points will re'- ceive-afpotential above ay predetermined value', means to applysaid voltage transitiontosaid gating lock'iin reciproconductive circuit to block said astable reciproconductive circuit;` thereby leaving the output reciprocondu'ctive cr-` cuitsr; with: the proper' binary code ctnnbination`v forl the character to. be:translated.asfexpressedfin` said other'code;

a switching;elementy interposed betweeny saidlastablierecipv 12 roconductive circuit and the countingY chain comprising' said' plurality of' bistabler reciproconductive circuitsI and'- counting chainl comprising said number of bistablei recipif roconductive. circuits to apply the output pulsesI of theastable reciproconductive circuit selectively to said chains',

meansv toreset saidY input reciproconductive circuitsv to theA initial condition, said means including further means connected to said gating lock-inY reciproconductive circuit to resetl said output reciproconductive circuits to a predetermined condition, a validityy checking circuit comprising input and output terminals, a connection' from the input terminal of said validity checking circuit to each offsaid plurality ofreciproconductivecircuits, means bias ing said validity circuit to produce current' at said outputI terminal upon the state of conduction of saidreciprm conductive circuits, failure to represent ay valid character. combination, and means to apply said current to sai'd lock-in reciproconductive circuit to control the operation' ofsaid astable reciproconductive circuit.

2. A reversible code translating circuit arrangement, in'- cluding' a plurality of storage circuits, there' being one' such circuit for each element of a character as expressed' in the code to be translated, means responsive to code signals expressed in the code to be translated, to trigger" said circuits in accordance with the nature ofthe signal. elements ofthe character to be translated, a number of: bistable reciproconductive circuits, there being one such. reciproconductive circuit for each element'of a character asexpressed in another code, an astable reciproconduetive circuit, a gating lock-in reciproconductive circuit coupled* to said stable reciproconductive circuit, normally holding the latter inoperative by an applied" holdingvol'tage, a source of operate or convert pulses' synchronized with the' utilization apparatus, meansV to applyv saidV operate or convert pulses to said gating reciproconductive circuit to remove said holding' voltage and permit said astable reciproconductive` circuit't'o run freely, a. plurality of coincidence points, a plurality of resistive elements connected to coincidence points, 'a plurality of plural electrode electron flow path devices' connecting said coincidence points to said astable reciproconductive circuit, means to apply thek output of said astable reciproconductivetcircuit` to said bistable reciproconductive circuits connected as ay binary chain, saidl reciproconductive cir.- cuits producing voltages whereby a single one of said coincidence points will receive a` potential. above a predetermined" value, means to applyl said voltage transition to said gating lock-in reciproconductive circuit to block said astable reciproconductive circuit,l thereby leavingthe reciproconductive circuits with thev proper binary code combination for the character to be translated as expressed' in said other code, means to reset said storage circuits to the initial condition, said means including fur.- ther means connected to said gating lock-in reciproconductive circuit to reset said reciproconductive circuits. to a predetermined-condition, a validity checking circuit comprising input and output terminals, a connection from the input` terminal' of said validity checking. circuit to each of'sa'id plurality of reciproconductive circuits,.means biasing said validity circuit to produce current atv said outputterminal upon the state ofr conduction of said re ciproc'onductive circuits, failure to. representa valid character combination, and meansl to apply said current to.y

cade to form a binary counting chain having acounting plural electrode devices having one electrode connected to the associated junction point, means coupling other electrodes of all of said controlled electron ow path devices to said electronic gating circuit, means to apply an operate pulse to said electronic gating circuit to start said pulse generator and step said counting chain through the cycle of conduction changes until coincidence current at one of said junction points is applied through the associated controlled electron tlow path device to said gating circuit to stop said pulse generator, thereby leaving said counting chain in a condition representative of the code character under consideration as expressed in said predetermined code.

4. An electronic code translating circuit arrangement, including a plurality of storage devices one for each signal element of a character as expressed in a given code arranged to be energized in one of two conditions in accordance with the nature of the signal element-of the character under consideration assigned to the storageelement under consideration, a plurality of bistable reciproconductive circuits one for each signal element of a character as expressed in a predetermined code, said bistable reciproconductive circuits being connected in 9 cascade to form a binary counting chain having a counting input, a generator arranged to produce a continuous train of pulses and being coupled to the counting input of said binary counting chain, an electronic gating circuit coupled to said generator to control the starting and stopping of the same, a plurality of resistive elements interconnected between said storage devices and said bistable reciproconductive circuits in permutations at which a number of junction points are established equal to the number of characters desired to be translated between said codes, a plural electrode controlled electron ow path device for each of said junction points, each of said plural electrode devices having one electrode connected to the associated junction point, means coupling other electrodes of all of said controlled electron flow path devices to said electronic gating circuit, means to apply an operate pulse to said electronic gating circuit to start said pulse generator and step said counting chain through the cycle of conduction changes until coincidence current at one of said junction points is applied through the associated controlled electron flow path device'to said gating circuit to stop said pulse generator, thereby leaving said counting chain in a condition representative of the code character under consideration as expressed in said predetermined code.

5. An electronic code translating circuit arrangement as defined in claim 4 and wherein said storage devices comprise further bistable reciproconductive circuits.

6. An electronic code translating circuit arrangement as defined in claim 5 and wherein said further bistable reciproconductive circuits are connected in cascade to form a further binary counting chain having a counting input and there are means provided to switch said pulse generator from the first said counting chain to said further counting chain to translate characters between said codes in opposite directions.

7. An electronic code translating circuit arrangement, including a plurality of storage devices one for each signal element of a character as expressed in a given code arranged to be energized in one of two conditions in accordance with the nature of the signalelement of the. character under consideration, a plurality fof bistable reciproconductive circuits one for each signal element of a character as expressed in a predetermined code, said v. bistable reciproconductive circuits being connected in cascade to form a binary counting chain having a counting input, a generator arranged to produce a continuous train of pulses and being coupled to the counting input of said binary counting chain, an electronic gating circuit coupled to said generator to control the starting and stopping of the same, a plurality of resistors interconnected between said storage devices and said bistable reciproconductive circuits in permutations at which a number of junction points are established equal to the number of t characters desired to be expressed in either of said codes, t

la plurality of diode devices-one for each of said junction points and having one electrode connected thereto, means coupling the other electrodes of all of said diode devices to said electronic gating circuit, means 'to apply an operate pulse to said electronic gating circuit to start said pulse generator and step said counting chain through the cycle of conduction changes until coincidence current at one of said junction points is applied through the associated diode device to said gating circuit to stop said pulse generator, thereby leaving said counting chain in a condition representative of the code character under consideration as expressed in said predetermined code.

8. In a code translating circuit arrangement for translating a protected code having a predetermined ratio ot v signal elements of one nature to signal elements of another nature, a pair of electron discharge devices each having cathode, control and anode electrodes, a plurality of current limiting elements connecting the control electrode of one of said electron discharge devices to each of a plurality of circuit points arranged to be energized in correspondence with said signal elements of one nature, another plurality of current limiting elements connecting the control electrode of the other of said electron discharge devices to another plurality of circuit points arranged to be energized in correspondence with said signal elements of another nature, means biasing said electron discharge devices to cut-off when said circuit points are energized in correspondence with said predetermined ratio of said signal elements, one of said electron discharge devices being further biased to conduct when said circuit points are energized in correspondence with a smaller ratio of signal elements, and the other discharge device being biased to conduct when said circuit points are energized in correspondence with a larger ratio of signal elements, and an output circuit connected between the anode electrodes and the cathode electrodes of said electron discharge devices.

9. In a code translating circuit arrangement for translating a protected code having a predetermined number of signal elements of one nature, a pair of electron discharge devices each having cathode, control and anode electrodes, a plurality of resistors connecting the control electrode of one of said electron discharge devices to each of a plurality of circuit points arranged to be energized in correspondence with said signal elements of said one nature, another plurality of resistors connecting the control electrode of the other of said electron discharge devices to another plurality of circuit points arranged to be energized in correspondence with said signal elements of another nature, means biasing said electron discharge devices to cutot when said circuit points are energized in correspondence with said predetermined number of signal elements of one nature, one of said electron discharge devices being further biased to conduct when said circuit points are energized in correspondence with a lesser number of signal elements of said one nature, and the other discharge device being further biased to conduct when said circuit points are energized in correspondence with a greater number of signal elements of said one avances v nature, andan output circuit' connected to the anodey electrades` of said electron discharge devices.

1'0; In a code' translating circuit arrangement for translating a protected' code having a predetermined'ratioy of marking elements to spacing elements, a pair of elcctron discharge devices each having cathode, control' and anode' electrodes, a plurality of resistors connecting the control electrode of one of said electron discharge devices' to each of a plurality ofcircuit points arranged to be energized in correspondence with marking si'gnal elements, another plurality of resistors connectingl the control' electrode off the other of'said electron discharge devices to another plurality of. circuit points arranged to be energized in. correspondence with spacing. signal". elements,A means. biasing said" electron discharge devices to cuteoff when said circuit4 points are energized in cor; respondence with said' predetermined number ratio ofi marking to spacing elements, one of said electron dis.- cha'rge devices beingfrther biasedto conductwhensaid circuit points are energized in correspondence with a. srnaller ratio of markingA to spacing elements, and. the other discharge device. being' further biased to conduct when said' circuit points; are energized in correspondencewith a' larger ratio ofmarking to spacing.elements,. and anelectronic output gatingcircuitconnected to the anode. electrodes to be energzedin the absence of. said. predetermined'ratio of 'marking to spacing signal. elements.

Il. In a cod'e translating, circuit arrangement,.inc1ud ing al plurality of bistable reciproconductive. circuits,l there being one such reciproconductive. circuit. for each. element of a character as expressed.V in. the translated code, means responsive to. the leading edge ofA a. reset:- pulse signal to trigger; said. reciproconductive circuits to the. initial condition of conduction, said means includingA further means responsive to. thetrailng, edge of said resetl pulse signal. to reset. certain. ones of said reciproconductive circuits. to a predetermined condition of. con-` duction other` thansaid initial. condition.

12. In a' code translating circuit arrangement. asdefined in claim 1.1. and wherein said bistable reciproconductive circuits each comprise a pair of cross-coupled' electron discharge devices having cathodes andt grids with` individual grid resistors andwherein said means tol reset said reciproconductiver circuits comprise a. normal-- 1y conductingA electron discharge. structure having cathode, control; and anode electrodes, a further normally conducting electron discharge structure. having. cathode,. control', and anod'e electrodes,. all'. of said grid resistors of-` one electron discharge dev-ice of each. reciproconductive circuit being connected" to the anode of the iirstA electron discharge structure and the grid resistors. of they other electron discharge device of a portion of said reciproconductive circuits being connected tov theV anode ofV said further electron dischargev structure, anda. capacit'or connected across said fur-ther electron. discharge structure, thereby to render all. of'said. grids positive with. respect t'o the respective cathod'es inresponse. to the: lead.-

ing, edgeofthe reset pulse applied tosaid grid" electrodesy ofi' said electron discharge structures to establish said' initial condition and' to render' said other grids positive with respect t'o the associated' cathode toreverse the" corresponding reciproconductive circuit' and establish a given` character in said circuits in response' to the trailing edge of said reset pulse.

13:. A code translating circuit arrangement including' a plurality of signal" element' storage' devices having inpnt coding terminals, a number of signal element storageI circuits having output coding'. terminals, means to apply signalA elements of a code character to be translated to the* coding terminals ofr said' signal element storage devices to" energize' the same individually in accordance with the' nature' of the signal element assigned;r means to" cyclicallyy energize said signal element storage circuits in' all possible combinations and' pernruta tionsl of' the naturel ofy signall elements assignable, detector circuitry connected between said storage devices' andE said storage circuits t'o determine coincidence be'- ,tween the character under consideration as established' in said storage devices andasestablished' in said storage' circuits and' means: coupled fromA said detector' circuitry' to said cyclically energizing means to' stop' said cyclically energizing means upon determination of co"- incidence by saiddetector circuitry;

I4; A code translating-circuit arrangement as dened; in claim 131 andl incorporating' means in conjunction with said cyclically energizing means to energize said storage devices and* said storage circuits selectively` wherebyl signal elements ofa character establishedl at the' in'gterminals ofl said storage devicesin' one code corre*- spond tothel signal character elements established at" the codingJ terminals ofI said storage" circuits and con"- verselyf.l

References (Ztd in the tile' of this patent UNITED STATES'- PATENTS.

2,397,604' Inlantleyr i i-. Apr. 2,; 1946'. 2533242'. Gridleyl .a Dec 1'2; 1950. 2,61057-'931 Krause: Sept.4 1.6; 1952` 2,668,870 Ridlen Febr. 9', 19544 2,675,538` Malthane'r Apr; lf3;- 1954v 2 ,6.82,5.73Y Hunt June 29,'. 1954 207473994V Dickensonietf al Sept. 113,1955.

Brown- Ian; 2,. 1'945.' 

